Means for switching wall attachment fluidic devices

ABSTRACT

An improved bistable device having atmospheric switching ports communicating with each outlet passage and the atmosphere external to the device. The switching ports connect with the outlet passages at the ends of attachment walls upstream of vent ports, and (the switching ports) enable the output state of the device to be switched by fluid control signals whose pressures are not affected by output loading conditions.

0 United States Patent nu 3,590,842

[72] Inventors Lynn G. Amos 3,187,763 6/1965 Adams l37/8l.5 Powell,Tenn.; 3,225,780 l2/l965 Warren et al .1 l37/8l.5 Hal L. Moses, Raleigh, N.C.: Donald A. 3.267947 8/1966 Bowles 137/81 .5 SmalLCastine. Maine 3,270,758 9/1966 Bauer l37/8l.5 [21] Appl. No. 812,666 3,275,013 9/1966 Colston 137/815 [22] Filed Apr. 2,1969 3,380,655 4/1968 Swartz l37/8l.5 X [45] Patented July 6, 1971 3.457935 7/1969 Kantola l37/8l.5 I73] Assign gami g Primary Examiner-Samuel Scott Attorneys-Clarence R. Patty. Jr. and Walter S. Zebrowski [54] MEANS FOR SWITCHING WALL ATTACHMENT FLUlDlC DEVICES 4Clai 1D F ABSTRACT: An improved bistable device having atmospher- U-S- 1. ic witching ports communicating each ouuet passage it. and the atmosphere externai to the device The switching Search orts connect the outlet passages at the ends of at. tachment walls upstream of vent ports, and (the switching [56] References cled ports) enable the output state of the device to be switched by UNITED STATES PATENTS fluid control signals whose pressures are not affected by out- 3.181,546 5/1965 Boothe 137/8l.5 put loading conditions.

CONTROL I POWER STREAM INPUT PATENTEUJUL BIB?! 0842.

CONTROL SIGNAL INPUT POWER STREAM INPUT mvswrms. L nn 6. Amos 0/ L. Moses Donald A. small ATTORNEY MEANS FOR SWITCHING WALL ATTACHMENT FLUIDIC DEVICES BACKGROUND OF THE INVENTION A typical wall attachment fluidic device used in the prior art embodies an interaction chamber defined by an end wall and two outwardly diverging sidewalls. A power nozzle in the end wall is provided for issuing a well-defined fluid power stream, having relatively high energy, into the chamber. A wedgeshaped flow divider is disposed downstream of the power nozzle with the apex of the divider being on the centerline of the power nozzle and the left and right sides thereof being generally parallel to and spaced from the sidewalls. The sides of the divider and the sidewalls of the chamber define a pair of fluid outlet passages, the fluid flow in one or the other passages representing the output state of the device.

Control of the output state is obtained by supplying a fluid control signal of relatively low energy with respect to the energy of the power stream to either of a pair of control nozzles or ports disposed on each side of the power nozzle and adapted to 'direct a fluid control stream into the power stream at a right angle thereto. A pressure differential across the control ports is used to directionally displace or deflect the power stream away from the centerline of the power nozzle and into one of the outlet passages.

Following such a deflection, the pressure in the region between the stream and the sidewall leading to or partially defining that passage is lower than the pressure in the chamber on the opposite side of the power stream. This region is normally referred to as the low-pressure region or the separation bubble. The pressure differential thus established across the power stream tends to induce a further deflection of the power stream in the direction in which deflection was initiated by the control signal. It is self-sustaining and remains even after the pressure differential between the control ports has been removed. In accordance with the well known Coanda effect, the deflected power stream strikes a sidewall of the chamber at a predictable distance downstream from the power nozzle, depending on such factors as the pressure of the power stream and the load impedance into which it flows, and thereafter becomes fully entrained into the outlet passage. The intersection point between the power stream and the wall is normally referred to as the point of attachment and the portion of the sidewall along which the attachment point can exist is called the attachment wall.

However, it was found that whenever the outlet passage in which the deflected power stream was entrained, i.e. the active outlet passage, was blocked or nearly so, the power stream, having no place to exit from the passage, would deflect into the other passage in the event the latter was relatively free of obstruction. Thus, it was found that heavy loading on the active outlet passage produced an often unintended and undesirable change in the output state of the device. If, on the other hand, both outlet passages were heavily loaded or blocked, the resulting back pressure built up in the interaction chamber by the fluid therein would shut off the further issuance of fluid from the power nozzle.

To overcome these difficulties, vent ports were added to each outlet passage which communicate with the atmosphere external to the device. These vents are located downstream of the attachment wall, often near the upstream end of the outlet passages and, due to their low fluid resistance, readily permit the power stream entrained in the active passage to be vented to the atmosphere when that passage is blocked or heavily loaded. Thus, regardless of the active passage output loading conditions, the power stream remains entrained therein, and the desired output state of the device is maintained.

However, though this problem of undesirable switching was eliminated by the use of vent ports, another difficulty persisted. Whenever a heavily loaded condition existed on the active outlet passage, .a considerably higher control port signal pressure was required in order to change the output state of the device than when the active passage was unblocked or lightly loaded.

The reason for this can be appreciated by visualizing the operation of the device under heavily loaded conditions. Since all of the fluid contained in the power stream is being vented to the atmosphere through the vent port, the stream remains attached to the wall. In order to switch to the other output state a control signal must be applied to the control port which communicates with the separation bubble in suflicient quanti- ,ty to overcome the pressure differential existing across the power stream. As fluid from the control port rushes into the low-pressure region, the point of attachment of the power stream shifts progressively downstream along the attachment wall until it reaches the vent port. However, because of the outflow of fluid through the vent port, no atmospheric fluid can inrush into the bubble in order to assist the control signal in raising the pressure thereof. Thus under blocked load conditions the control port must supply all the flow increase to separation bubble necessary to neutralize the pressure differential existing across the power stream. On the other hand, when the active passage is unobstructed, no fluid is vented from the vent port to the atmosphere and atmospheric fluid is free to become entrained into the vent and into the separation bubble in order to assist the control signal neutralizing the pressure differential. Because of this problem, the'minimum control signal required to produce output state switching of these devices is a function of output loading. Higher control signal pressures are requiredto switch the device under heavily loaded active outlet passage conditions than under light loading conditions. Furthermore, the time required to switch the device from a heavily loaded output state to another output state after the required control signal has first been applied is significantly greater than the switching time under light loading conditions.

SUMMARY OF THE INVENTION It is therefore an object of the instant invention to provide an improved fluidic wall attachment device which overcomes the aforementioned difficulties.

It is yet another object of the instant invention to provide an improved fluidic wall attachment device having a faster switching response time under heavily loaded output conditions than has heretofore been obtainable.

It is still another object of the instant invention to provide an improved fluidic wall attachment device in which the effect of a given control port fluid signal pressure on the power stream is substantially constant regardless of output loading conditions.

Briefly, in accordance with the instant invention, an improved fluidic wall attachment device is provided. Conventional wall attachment devices include a power nozzle for issuing a stream of fluid into an interaction chamber, means for effecting the directional displacement of the stream, plural outlet passages for receiving the fluid, and fluid-venting means communicating with the passages and a predetermined atmosphere. The improvement of the instant invention comprises at least one atmospheric switching port communicating with both a predetermined fluid atmosphere and at least one of the outlet passages upstream of the venting means.

Additional objects, features, and advantages of the instant invention will become apparent to those skilled in the art from the following detailed description and attached drawing on which, by way of example, only the preferred embodiment of the instant invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE shows a plan view of an improved fluidic wall attachment device. illustrating the preferred embodiment of the instant invention.

3 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the FIG. there is shown an improved wall attachment fluidic device 10 having a power nozzle 12 issuing a wellidefined power stream, represented by arrows, into an interaction chamber 14. A wedge-shaped flow divider I6 is disposed downstream of the nozzle 12, the sides of which separate and partially define a pair of fluid outlet channels or passages 18 and 20, respectively. The output states of the device 10 can be switched by supplying fluid control signals of suitable pressure to a pair of control nozzles or ports 22 and 24 in a usual manner. A pair of vent ports 26 and 28 respectively communicate with the passages 18 and 20 near the downstream ends thereof as shown and are adapted in any well-known manner to offer a low resistance to the flow of fluid therethrough to the atmosphere external to the device 10 when the passages 18 and 20 are blocked or heavily loaded.

A air of atmospheric switching ports 32 and 34 communicate with the atmosphere external to the device 10 and with the passages 18 and 20 respectively. The position of the openings of the ports 32 and 34 into the passages 18 and 20 define the downstream ends of a pair of attachment walls 36 and 38 respectively. For illustrative purposes a plunger 40 is shown in a retracted position away from the downstream end of the passage 18. This position represents an unloaded condition with respect to the flow of the power stream in the passage 18. On the other hand, when the plunger is advanced to a position blocking the downstream end of the passage 18, as represented by dashed lines 42, the condition of heavy or blocked loading of the power stream flow in the passage 18 exists.

The following is a typical example of the operation of the device 10. Assume that the power stream issuing from the nozzle 12 is attached to the wall 36 and is thereby fully entrained into the passage 18 as shown. In the retracted position of the plunger 40, the downstream end of the passage 18 is unobstructed such that the power stream is unloaded and flowing through the downstream end of the passage 18. Under this condition a pressure differential forces the power stream to maintain its attachment to the wall 36, and a region 44 of low pressure relative to atmospheric pressure exists. Now the power stream in the active passage 18 is fully loaded by shutting off the downstream end of the passage 18 by advancing the plunger 40 to the position 42. Because of the relatively low resistance of the vent port 26 to fluid flow, the fluid contained in the power stream is readily vented to the atmosphere as illustrated. Thus, the power stream remains entrained in the passage 18 in a stable manner.

Now, assume that it is desired to change the output state of the device l under this loaded condition of the active passage 18 by switching the power stream to the other passage 20. To accomplish this, a fluid control signal is introduced, under pressure, into the control port 22 which thereafter rushes into the low-pressure region 44 in the chamber 14. As the fluid of the control signal fills the region 44 the attachment point, represented by a point 46, shifts progressively downstream along the wall 36 until it reaches the switching port 32. The static pressure in the region 44 being below atmospheric pressure, no fluid from the power stream-is lost to the atmosphere through the switching port 32. However, since the port 32 now communicates with the low-pressure region 44, atmospheric fluid, at a higher pressure relative to the region 44, is entrained into the port 32 and rushes into the low-pressure region 44.

Thus, once the attachment point of the power stream reaches the port 32, the higher pressure atmosphere external to the device is utilized to assist the control signal at the port 22 in overcoming the pressure differential existing across the power stream. The low-pressure region 44 thereby rapidly disappears and attachment of the power stream to the wall 36 is broken. Once the pressure differential across the power stream is overcome, a control signal of low pressure introduced at the port 22 is sufficient to create a pressure differential across the power stream in the opposite direction so as to deflect it into the passage 20.

The prior art devices having a vent similar to the port 26 but not a switching port similar to the port 32 required greatly increased control signal pressures in order to change the output state of the device when the active outlet passage thereof was blocked or heavily loaded. Since the vent port offered little resistance to the escape of fluid to the atmosphere, when the active outlet passage was blocked, the fluid of the power stream completely filled the vent thus not permitting the external atmosphere to communicate with the low-pressure region. Consequently under blocked load conditions the control signal had to overcome the pressure differential across the power stream without assistance. This required a high pressure control to produce output state switching where the active outlet passage was subjected to heavily loaded conditions. However, since little or no fluid was vented through the vent port of the active passage during lightly loaded conditions, atmospheric fluid at high pressure could inrush into the low-pressure region once the control signal had shifted the attachment point sufficiently downstream to engage the vent port. Thus under light loading conditions of the active passage, the required control signal at the control port was low.

In the instant example of the present invention, the addition of the atmospheric switching ports 32 and 34 to the device 10 renders the fluid signal pressure at the control ports 22 and 24 required to produce output state switching, substantially constant under any possible condition of loading on the active passage. Further, the control signal pressure level required to switch the device 10 under any loading conditions on the active passage is of the same order as the pressures required to switch the prior art devices under unloaded conditions, Le. a relatively low pressure. The outwardly diverging flare of the ports 32 and 34 as shown in the illustration are not an essential feature of the invention but merely a routine design consideration which will be readily apparent to those skilled in the art. The essential features of the ports 32 and 34 are as has previously been explained, that atmospheric fluid external to the device 10 be readily entrainable therethrough into the passages 18 and 20 when the low-pressure region of the chamber 14 communicates therewith, and that the ports 18 and 20 do not operate as fluid vents under heavily loaded output state conditions. It should be noted that if the resistance of the ports 32 and 34 is too low, on the order of the resistance of the vent ports 26 and 28, the ports 32 and 34 may entrain atmospheric fluid into the power stream so as to appreciably increase the volume of fluid flow of the power stream in the active passage. This however may be desirable in cases where the device 10 is designed to function as a flow amplifier rather than in the more usual case, as a pressure amplifier. Note too that the vent ports 26 and 28 should be large enough to permit sufficient venting of the fluid in the passages 18 and 20 so that no substantial back pressure is transmitted upstream to a point adjacent the switching ports 32 and 34. Should this occur and should the magnitude of back pressure exceed atmospheric pressure then quite clearly the ports 32 and 34 would act as an additional set of vent ports. This would therefore not permit atmospheric fluid outside of the ports 32 and 34 to inrush into the region 14 so as to raise the pressure level of the region 44 and aid in output state switching.

Although the instant invention has been described with respect to specific details of a certain embodiment thereof it is not intended that such details limit the scope of the instant invention except insofar as set forth in the following claims.

We claim:

1. In an improved fluidic wall attachment device of the type comprising a power nozzle for issuing a power stream of fluid into an interaction chamber,

control means for effecting the directional displacement of said stream,

at least two outlet passages located downstream of said nozzle for receiving said fluid, and

fluid-venting means communicating with said outlet passages and a predetermined fluid atmosphere, the improvement comprising one atmospheric switching port communicating at one end with said predetermined atmosphere and connected at the other end to one of said outlet passages upstream of said venting means, there being a high impedance to said power stream fluid tending to flow through said switching port and a relatively low impedance, as compared to said high impedance, to fluid tending to flow therethrough from said predetermined atmosphere to said one outlet passage.

2. In the device of claim 1 wherein said one atmospheric switching port comprises a passage defined by sidewalls diverging toward said other end which communicates with said one outlet passage.

3. In the device of claim 1 a second atmospheric switching port communicating at one end with said predetermined atmosphere and connected at the other end to the other of said outlet passages upstream of said venting means.

4. In the device of claim 3 wherein said second atmospheric switching port comprises a passage defined by sidewalls diverging toward said other end which communicates with said other of said outlet passages. 

1. In an improved fluidic wall attachment device of the type comprising a power nozzle for issuing a power stream of fluid into an interaction chamber, control means for effecting the directional displacement of said stream, at least two outlet passages located downstream of said nozzle for receiving said fluid, and fluid-venting means communicating with said outlet passages and a predetermined fluid atmosphere, the improvement comprising one atmospheric switching port communicating at one end with said predetermined atmosphere and connected at the other end to one of said outlet passages upstream of said venting means, there being a high impedance to said power stream fluid tending to flow through said switching port and a relatively low impedance, as compared to said high impedance, to fluid tending to flow therethrough from said predetermined atmosphere to said one outlet passage.
 2. In the device of claim 1 wherein said one atmospheric switching port comprises a passage defined by sidewalls diverging toward said other end which communicates with said one outlet passage.
 3. In the device of claim 1 a second atmospheric switching port communicating at one end with said predetermined atmosphere and connected at the other end to the other of said outlet passages upstream of said venting means.
 4. In the device of claim 3 wherein said second atmospheric switching port comprises a passage defined by sidewalls diverging toward said other end which communicates with said other of said outlet passages. 